Method and apparatus for metal coating



Oct. 12, 1937. v A. c. SIMMONS METHOD AND APPARATUS FOR METAL COATING Filed March 13, 1935 2 Sheets-Sheet l J 12, 1937- A. c. SIMMONS 2,095,718

METHOD AND APPARATUS FOR METAL COATING 7 Filed March 15, 1935 2 Sheets-Sheet 2 a 27 1 W Z6 29 l u {I ll 35 L u L H z9 12 54 v .34 12' v 82K? n 'l 1 1 [19 III. ,3 1| z\:-- 51 v J 26 &g

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Patented Oct. 12, 1937 PATENT OFFICE METHOD AND APPARATUS FOR METAL cos'rmc 1 Andrew 0. Simmons, Monessen, Pa.

Application March 13,

14 Claims.

This invention relates to what may be termed a roller-wipe, i. e., to theemployment of an apparatus which serves to confine a bath of molten coating metal and provides means acting on said coating metal to remove extraneous substances from its surface, commonly known as skimmings and dross, at the position where the coated material, preferably wire and woven wire products, emerges from said bath, in order to keep the coating metal clean at this point and eliminate the necessity for the use of protective headers or coverings of charcoal, sand or oil.

It is an object of the invention to entirely eliminate mechanical means for smoothing or removing excess coating metal and reduce the coating cost by the control of the quantity of coating applied within limits heretofore unattainable, which thus reducesthe cost of the finished product. In the ensuing description I shall explain the invention with reference to wire and zinc as the treated and treating materials, respectively; and, although my invention is particularly adapted for use with such materials it should be understood that it may possibly be employed advantageously with other materials as well.

With these and other objects not specifically mentioned, the invention consists in certain constructions and combinations which will be hereinafter fully disclosed and then specifically set forth in the claims hereunto appended.

The method involves the use of rollers which are partially immersed in the bath of molten metal, and which provide for the trapping or confining of a body of coating metal between the roller surfaces at the point where the wire or other product emerges. The wire thus receives its final coating and emerges from a relatively small body of entrapped metal which is freed from the heavier skimmings and thus maintained in a relatively clean or bright condition. This protection is afforded by interfitting flanges on the rollers which serve to exclude the heavy skimmings and prevent them from entering the space between the rollers, which thus provides a confined body of molten metal having a sufliciently restricted surface area between the rollers to afford a meniscus surface between the emerging wire and the contiguous roller walls.

The present method also includes the subjecting of the meniscus surface to variable and unequal movements of the roller surfaces, which results, in a breaking up or dislodgment of any floating particles which may accumulate at points closely adjacent to the emerging wire or wire 1936, Serial No. 68,593

products, and which are thus withdrawn toward the roller surfaces so that thedanger of their deposition upon the emerging wire is avoided. It has been found that by rotating one of the rollers by the friction of the emerging wire, and by allowing the other roller to rotate in a variable manner, and by permitting slight longitudinal movement of one of the rollers to occur, it is possible, without the employment of other separate or special instrumentalities, to dislodge floating particles from points adjacent to the emerging wire or wire products and direct their movement toward the roller surfaces, thus improving the character and quality of the coating.

As illustrative of an apparatus adapted to carry out the method of the present invention, reference is had to the accompanying drawings, wherein,

Figure 1 is a plan view of the apparatus showing the rollers and a portion of the framework partly in section;

Fig. 2 is a sectional view taken on line Fig. 1;

Fig. 3 is a sectional view taken on line 3-3 of Fig. 1;

Fig. 4 is an enlarged sectional detail of the rollers showing the interfltting of the end flanges to block off and entrap the limited body of coating material from which the wire or wire products directly emerge during the coating operation;

Fig. 5 is a diagrammatic view-showing the rollers in section and showing the formation of the meniscus surface between the emerging wire and the contiguous roller surfaces; and r Fig. 6 is a detail of one of the steady blocks for positioning the journals of the rollers.

The apparatus includes a tank or receptacle ill for the molten metal, which will ordinarily be zinc or a composition thereof. Within the receptacle is located a rectangular frame II which isopen at the top and bottom, the lower portion of which is immersed into the molten metal in the receptacle Ill. The frame II is provided with flanges l2 and IS, the latter of which may rest upon rails extended along the tank top, which furnish a support for the partially immersed frame. The frame ll affords a mounting for journal bars l5, one on each side of the frame, which 'journal bars serve to support the ends of roller shafts I6 and I1, each of the shafts being reduced at its end in the form of a trunnion to receive a steel collar l8 which rotates upon the proximate journal bar. As shown, each collar may be welded as at a to the shaft end, permitting its replacement, when necessary, by first turning off the collar end to break the weld for removal of the collar preliminary to substitution of a fresh collar.

The shaft l6 mounts the roller l9 having heads 20 provided with marginal flanges 2| and inner grooves 22, and the shaft l'l mounts the companion roller 23 having heads 24, each of which is provided with a circumferential flange 25, which flanges 25 lap the flanges 2| and enter in greater or less degree into the grooves or channels 22, as best shown in Fig. 4.

The surface of the roller 23 is pressed toward the surface of the roller I! by the provision of levers 26 pivoted by bolts 21 to bridge bars 28 which rest upon the standards 29 projecting upwardly from the journal bars I5. The outer arms of the levers 26 are drawn downwardly by springs 30. The roller I9 is provided at each end with a hardened steel trunnion collar 3|, which contacts a back bearing block 32 carried by a steady block 33 suspended by threaded hangers 34 with cooperating nuts 35 engaging the bridge bar 28. These collars may be secured as by welds b, permitting replacements conveniently in the same manner as for the collars l8. Similar steady blocks 36 bear upon the ends of the shaft I! which carries the roller 23. The arrangement is one which permits vertical adjustment of the steady blocks to compensate for wear of the collars l8, and permits the rollers to be easily removed either individually or in conjunction with the frame of the roller mounting, which can be removed as a unit for purposes of cleaning or otherwise.

As shown, the driven roller 23 is provided with spiral grooves or channels 31 of relatively steep pitch, although the employment of such surface configurations is optional and is not ordinarily required. It is important, however, to provide for a limited freedom of longitudinal movement between the rollers, and for this purpose the width of the grooves 22 will be slightly greater than the thickness of the entering flanges, so that there may be a very limited end play between the rollers, so small, in fact, that one surface of each flange will more often than not'be in driving engagement with the associated groove. One of the rollers, that designated as l9, will be referred to as the driving roller, whereas the companion roller 23 will be referred to as the driven roller.

The wires W to be coated are drawn under tension through the molten metal bath under a sinker bar 38 and then upwardly through a quarter turn around the surface of the roller IS on their way to take-up reels (not shown). A very considerable drag or friction is thereby imparted to the roller surface causing the roller to rotate uniformly with a surface speed equal or substantially equal to the linear travel of the wires being coated. The companion roller, however contacts the wires only at the biting line and thus is variably subjected to the friction of the wires, which variable friction is supplemented by the variable contact between the overlapping roller flanges which move into and out of frictional contact in a more or less uncertain or variable erratic manner, with the result that uniform motion of the driving roller will be imparted variably and unequally to the driven roller. This feature permits the building up of a slight oxidized surface, and due to the difference in the meniscus which occurs when the speed of travel varies on the driven roller, there is a tendency for this oxidized skin to affect the surface tension and in that way permit the skin of oxide surface to be pulled away and over to the flux covered surface of the rollers.

If the speed were constant as would be obtained by the use of gears or other mechanical driving devices, there would be a tendency for the meniscus to remain'constant and due to. the fact that the meniscus prevents the oxidized surface from flowing up and making contact with the rollers, there would be a tendency for this oxidized material to remain entrapped between the two rollers. It is only due to the fact that the rollers become coated with a rough material commonly known as dross, and to the intermittent motion referred to above, that I, find it possible to keep the trough free, or relatively free, from an oxidized material which would eventually contaminate the surface of the products being coated.

The principal feature of the present process lies in withdrawing the wire from a bath of molten metal through a surface which has been skimmed or cleared of floating material commonly known as zinc skimming which are in effect particles of zinc oxide with occluded particles 'of metallic zinc and occasionally small crystalline particles of an iron zinc alloy known as dross, which sometimes, due to becoming entrapped in the lighter zinc oxide surface, will'float on the surface of the bath. This is then referred to as floating dross.

The coated wire, after being withdrawn through the cleared or skimmed surface, is not subjected to any other extraneous means of wiping or preforming the coating around the wire. The wire is preferably withdrawn vertically, and the rapidity of this withdrawal is governed by the surface tension of the molten zinc, which is maintained at a temperature sufficiently above the melting point'to assure continuous operation of a plurality of wires and below a temperature which would be excessively destructive to the container and other equipment. This temperature may be specified as between 800 and 925 F.

The coated wire is withdrawn through a cleared surface of fluid zinc and not subjected to the action of any wiping material or device whatsoever, depending entirely upon the fluidity or viscosity of the molten metal and the length of time which said wire was submerged during its continuous passage through the molten metal, and augmentingthis process by the feature of taking advantage of the surface tension of the molten metal, in relation to the wire being withdrawn and the proximity and size of the rollers used to maintain the clear surface.

The two rollers are so constructed that, although made of a metal heavier than molten zinc, a certain degree of buoyancy is obtained by v making them hollow and partially submerging these rollers in the molten bath and retaining their relative position by suitable bearings and tension devices readily understood by reference to the drawings which form part of this application.

The wire in its travel through the bath and out through the cleared surface imparts to the rollers a clockwise and counter-clockwise motion suflicient to remove from the surface of the molten metal entrapped between the two rollers any particles of extraneous material which may form on this surface. is a suitable flux for removing from their surface any extraneous material which they in turn remove from the surface of the cleared metal Backing up both rollers held between the rollers and through which the wire passes. The maintenance of this flux and its composition is well known to the trade.

Referring to Fig. 5, it will readily be seen that when the surface of metal retained between the two rollers is so adjusted that the rollers in their clockwise and counter-clockwise rotation confine their disturbing and withdrawing action to the meniscus surface of the metal closely adjacent to the roller surface, but do not extend the disturbance outwardly to the meniscus immediately surrounding the wire, the wire will become evenly coated and will not have any uneven or heavily coated sections upon its surface. Therefore, it will be readily understood that a proper selection of the size of the rollers relative to the wire being galvanized and the relative position of these rollers within the bath in relation to the level of such bath, determines to a large degree the smoothness and uniformity which may be obtained by this process of withdrawing the wire through a clear surface of molten zinc at such speed and under such conditions that the meniscus immediately around the wire remains substantially constant and is undisturbed by the travel of the wire, while the meniscus adjacent to the roller surfaces is subject to the disruptive effects of inequality and variation of motion with a resultant withdrawal of surface particles upon the surfaces of the rollers.

Although the invention has been described with accuracy as to detail, it will be understood that variations in the technique to be employed and in the nature of the apparatus utilized may be introduced without departing from theprinciple of the invention. It will also be understood that, although the present method is directed primarily to the application of a galvanizing coating to wire or wire products, it is not the intention to necessarily limit the coating to zinc, since the principles herein set forth may be applicable to coatings generally, and in particular to coatings which tend to oxidize or otherwise produce a surface skin or coating of the general character which is present in the employment of a galvanizing bath.

I claim:

1. The method of coating materials which consists in maintaining a body of the coating material entrapped between contiguous roller sur faces, drawing the material to be coated between the roller surfaces and through the body of entrapped coating material and out through the surface thereof in a manner to maintain a. meniscus surface between the roller surfaces and the emerging material being coated, and imparting unequal relative novement to the roller surfaces to subject the meniscus surface to the effects of variable movement and to cause skimmings thereon to be drawn away from the material being coated and deposit themselves upon the roller surfaces.

2. The method of coating materials which consists in maintaining a body of the coating material entrapped between contiguous roller surfaces, drawing the material to be coated between the roller surfaces and through the body of entrapped coating material and out through the surface thereof in a manner to maintain a meniscus surface between the roller surfaces and the emerging material being coated, imparting substantially constant movement to one of the roller surfaces and variable movement to the other roller surface, and thereby subjecting the meniscus surface to the effects of variable movement to cause withdrawal of skimmings thereon to the roller surfaces and away from the surface of the material being coated.

3. The method of applying a galvanizing coating to wire which consists in maintaining a body 5 of coating metal in molten condition entrapped between roller surfaces and passing the wire to be coated around one of said roller surfaces and in contact with the other roller surface at the point of closest proximity and up through the body of molten metal entrapped above said point and out through the surface thereof under conditions resulting in the formation of a meniscus surface between the emerging wire and the roller surfaces, and imparting unequal relative movement to the roller surfaces to subject the meniscus surface to the effects of such unequal movement to thereby dislodge skimmings upon the meniscus surface to cause the same to be deposited upon the roller surfaces and carried away from the wire at its point of emergence from the molten coating metal.

4. The method of applying galvanizing coating to wire'which consists in maintaining a body of coating metal in molten condition entrapped between roller surfaces and passing the wire to be coated around one of said roller surfaces and in contact with the other roller surface at the point of closest proximity and up through the body of molten metal entrapped above said point and out through the surface thereof under conditions resulting in the formation of a meniscus surface between the emerging wire and the roller surfaces, and imparting unequal and variable relative movement to the roller surfaces to subject the meniscus surface to theeifects of such unequal and variable movement to thereby dislodge skimmings upon the meniscus surface to cause the same to be deposited upon the roller surfaces and carried away from the wire at its 40 point of emergence from the molten coating metal.

5. The method of coating wire with a metallic coating which consists in drawing the wire upwardly from the coating bath under conditions which result in the formation of a meniscus surface adjacent the wire at its point of emergence and in subjecting said meniscus surface to unequal movement in proximity to the point of emergence of the wire to cause dislodgment of surface skimrnings and the withdrawal thereof from the emerging wire without disturbing the meniscus surface immediately in contact with the wire.

6. The method of coating wire which consists in confining a body of molten metal between surfaces closely contiguous to the wire and in withdrawing the wire through and out from the surface of said confined body of molten metal under conditions resulting in the formation of a mings and the withdrawal thereof from the surface of the emerging wire without disturbing the meniscus surface immediately in contact with the wire.

7. The method of coating wire which consists in confining a body of molten metal between up- "I0 wardly moving surfaces closely contiguous to the wire and in withdrawing the wire through and out from the surface of said confined body of molten metal under conditions resulting in the formation of a meniscus surface between the emerging wire and the contiguous confining surfaces, and in imparting unequal upward movements to the confining surfaces to subject the meniscus surface to the agitating effects of such unequal movements and cause displacement and withdrawal of surface skimmings away from the surface of the emerging wire.

8. In mechanism for coating materials, the combination of a receptacle for the coating material, contiguous rollers mounted within the receptacle in position to bring their upper surfaces above the level of the coating material therein contained, and means associated with said rollers for entrapping a body of the coating material between the rollers and above the point of closest proximity of the roller surfaces, said means consisting of overlapping? circumferential flanges on the respective rollers, and said flanges being spaced to allow limited relative longitudinal movement between the rollers.

9. In mechanism for coating materials, the combination of a receptacle for the coating material, contiguous rollers mounted within the receptacle in position to bring their upper surfaces above the level of the coating material therein contained, and means associated with said rollers for entrapping a body of the coating material between the rollers and above the point of closest proximity of the roller surfaces, said means consisting of overlapping flanges on the respective rollers, flanges on one of said rollers positioned to receivethe flanges of the companion roller, the width of said grooves being greater than the thickness of the entering flanges to permit limited relative longitudinal movement between the roller surfaces.

10. In combination with a receptacle containing molten metal through and from which a wire is drawn under tension, a roller wipe mechanism near the point of wire exit from the receptacle comprising a frame, a pair of side by side horizontal rollers having a mounting on the frame, the wire being carried below and partly around one roller to drive it while leaving the bath in a vertical direction and the other roller also receiving from the wire engagement at its peripheral point which lies close to the roller first named, an adjustable back bearing for the first named roller, means for exerting a force upon the second roller tending to advance it toward the first roller and against the wire which is disposed therebetween, and interfitting flangs at the roller ends so arranged as to permit of a slight .endwise movement of one roller with respect to the other.

11. In mechanism of the kind described, the combination of a receptacle containing fluid coating material, idle driving and driven rollers in contiguous relation within the receptacle and both arranged to rotate in part through the material therewithin, a mounting for the driven roller such that it may be shifted toward and from the driving roller, means urging the driven and grooves adjacent the roller into frictional contact with the driving roller, and means within the receptacle and below the intended level of the coating material for guiding work proceeding through the coating material and below the surface thereof in a substantially horizontal direction and then upwardly and between the rollers and around the driving roller through approximately 90 degrees whereby to impart a frictional pressure thereon reater than on the driven roller.

12. In mechanism of the kind described, the combination of a receptacle containing fluid coating material, a framework supported upon the receptacle comprising a pair of back bearings, an idle driving roller having end trunnions adapted to abut the back bearings, an idle driven roller also provided with end trunnions, both rollers being located within the receptacle in position to bring their lower surfaces below the intended level of the coating material, means acting on the trunnions of the driven roller urging it toward the driving roller and the latter against the back bearings, and means within the receptacle and located below the intended level of the coating material for guiding work proceeding through the coating material in a substantially horizontal direction and then upwardly between the rollers and around the driving roller for approximately 90 degrees whereby to impart a frictional pressure thereon greater than on the driven roller.

13. In mechanism for coating materials, the combination of a receptacle for the coating material, contiguous rollers mounted within the receptacle in position to bring their upper surfaces above the level of the coating material therein contained, and means associated with said rollers for entrapping a body of the coating material between the rollers and above the point of closest proximity of the roller surfaces, said means consisting of overlapping circumferential flanges on the respective rollers, and. said flanges being spaced to allow limited relative longitudinal movement between the rollers, and means for exerting pressure upon one of the rollers to press the same inwardly toward the other roller.

14. In mechanism for coating materials, the combination of a receptacle for the coating material, a frame removably mounted within the receptacle, journal mountings on said frame, a pair of contiguous rollers journalled within said journal mountings and in position to bring their upper surfaces above the level of the coating material contained within the receptacle, one of said rollers being forced under pressure toward the other roller, and means for entrapping a body of the coating material in the -space above the line of closest proximity of the roller surfaces, said means consisting of circumferential loosely interfitting flanges on the respective rollers adapted to permit relative longitudinal movement between said rollers.

ANDREW C. SIMIVIONS. 

